/Engine/Source/Runtime/Core/Public/Math/Quat.h
Subtracts another quaternion from this. This is a component-wise subtraction; composing quaternions should be done via multiplication.
reference to this after subtraction.
[TQuat](API\Runtime\Core\Math\TQuat)< T > operator-= ( const [TQuat](API\Runtime\Core\Math\TQuat)< T > & Q )